DYNAMIC-MECHANICAL AND LIGHT-SCATTERING STUDY OF THE GLASS-TRANSITIONOF POLY(VINYLACETATE) AND A POLY(VINYLACETATE) PLUS POLY(4-HYDROXYSTYRENE) BLEND

The dynamics of poly(vinylacetate) (PVAc) and of a blend of PVAc and 2 0% in weight of poly(4-hydoxystyrene) have been studied in the glass t ransition region using dynamic-mechanical and photon-correlation spect roscopies. Both kinds of data show the overlapping of the main alpha r elaxation with a faster one. The complex part of the elastic modulus s hows the existence of a beta' sub-T-g transition overlapping with the alpha and beta transitions. As a consequence, at least two Kohlraush-W illiams-Watts terms are needed to describe the relaxation functions. T he results show a good agreement with the predictions of the mode coup ling theory except for the fact that the calculated critical temperatu re seems to be lower than the calorimetric glass transition temperatur e.